The classes of polymers known as poly(p-phenyleneethynylene)s, or PPEs, and poly(p-polyphenylenevinylene)s, or PPVs, have found uses as active layers in light-emitting diodes, “plastic lasers,” light emitting-electrochemical cells, thin film transistors, and chemical sensors. Hybrid polyphenylenevinylene-ethynylenes copolymers, or “PPVEs,” having strictly alternating PPE and PPV monomeric units combine the physical (phase, thermal) behaviour of the PPEs/PPVs with a new class of optical properties, including enhanced electron affinity. This makes PPVEs incredibly promising candidates for use in transistors and other solid-state electronic devices. Their unique electronics can be easily tuned via the side chains, while retaining the well-understood solid-state phase behaviour, X-ray diffraction, and the like of the PPEs. Such PPVE polymers have been used for their charge carrier mobility, especially in anthracene-PPVE copolymers, electroluminescent properties, photovoltaic properties for use in solar cells, and as the active component in thin film field effect transistors.
Work on poly(thiophene)s has shown that the identity and relative position of side chains along a conjugated polymer backbone has a large impact on the properties of the resulting polymer. Normal polymerization methods incorporate all possible combinations into the backbone, producing an inherently regiorandom polymer. There are steric and (in some cases) electronic “clashes” between side chains which “point” towards each other, twisting the backbone out of planarity with corresponding effects on the effective conjugation length and overall polymer crystallinity. This is of great importance, not only for the poly(thiophene)s but for any rigid-rod conjugated polymer that experiences a similar occurrence.
Regioregular materials have higher crystallinity, red-shifted absorptions in the optical region, a greater conductivity, and (usually) a smaller band-gap compared to the regiarandom versions of the same polymer. This has direct and powerful implications on the use of these materials for electronic applications. These effects have been studied in poly(1,4-phenylenevinylene)s and poly(1,4-phenyleneethynylene)s, but not for PPVEs due primarily to a lack of a valid synthetic route to regioregular PPVEs.